In this project, we seek to identify novel epigenomic biomarkers on cord blood DNA that could be used to reconstruct at birth obesogenic fetal-life experiences and to profile risks of childhood obesity and related cardio metabolic phenotypes. We will use state-of-art technology for methylomic screenings of ~486K methylation sites on cord blood DNA from Project Viva, a pre-birth cohort with validated prenatal exposures since early pregnancy and multiple collections of child behaviors and phenotypes until age 12. We will first identify DNA methylation signatures correlated with fetal-life obesogenic risk factors, i.e. maternal obesity, high gestational weight gain, and low maternal intakes of polyunsaturated fatty acids (PUFAs) and vitamin D (Aim 1). We will then characterize DNA methylation signatures predictive of adverse post-natal trajectories of body weight, adiposity and cardio metabolic phenotypes from early life until 12 years of age (Aim 2). Finally, we will confirm the methylomic biomarkers identified in Project Viva in an independent replication set of mother- child pairs from a cohort (Generation R) with similar design and individual characteristics (Aim 3). Our project will also explore 5-hydroxymethylcytosine, an emerging and under-investigated form of DNA methylation, as a fetal-life biomarker. By taking advantage of prospective detailed data collections, we can also explore whether associations identified between methylomics and obesity-related outcomes are attenuated by healthful postnatal behaviors (lower consumption of sugar-sweetened beverages and fast food; lower TV/screen time; higher physical activity; age-appropriate sleep duration). If we were to reconstruct at birth the child's risk-factor experience during fetal life, and use such information to predict the risk of developing obesity later in life this would dramatically reduce the lag time before targeted educational and preventive measures can be instituted. The use of cord blood DNA as an epigenetic archive of prenatal environments is supported by recent human findings demonstrating that cord blood DNA methylation captures effects from in-utero exposures. Because it can be collected at birth from every newborn, cord blood DNA is ideal for immediate translation of scientific findings into prevention-directed actions. As the results of fetal programming can only be ascertained years after the exposure, investigating the effects of prenatal risk factors requires longitudinal studie with accurate fetal assessments and prospective repeated child phenotyping. Project Viva and Generation R, in which these measures have been collected, starting in early pregnancy with repeated measures until early adolescence, provide a unique cost-effective opportunity to achieve this objective.